I. Field of the Invention
The present invention relates generally to on-board fluid systems including hydraulic systems carried by heavy machinery such as transit concrete mixing trucks and, more particularly, to a tank arrangement for such fluids.
II. Related Art
Vehicle-mounted hydraulically-powered equipment for various use has become quite common. As an example, hydraulic operating systems are used to turn mixing drums on transit concrete mixing and dispensing vehicles and to operate auxiliary axle assemblies including tag axles and other hydraulic devices associated with the vehicle.
In the hydraulic system of the type carried on vehicles, a metal hydraulic fluid reservoir tank is typically utilized to store the hydraulic fluid used in the system. The fluid is pumped from the tank and circulated to operate various hydraulic devices and thereafter returned to the tank. During the operation of hydraulic devices, oil is constantly circulating through the system and through the tank. As many hydraulic devices operate at very high pressures, oil returned to the tank is often at an elevated temperature in comparison to the supply oil in the tank or reservoir. Thus, thorough mixing of the return oil with the stored oil within the tank is desirable to efficiently cool the hot returning oil which avoids overheating and enables it to achieve a maximum service life.
While existing designs of hydraulic tanks such as that shown in U.S. Pat. No. 5,076,703, assigned to the same assignee as the present application, have proven satisfactory, tanks which promote better mixing between return and stored fluid have been continually sought. In addition, because of the limited space on board a vehicle, more compact and improved location for auxiliary fluid reservoir tanks also presents an advantage with respect to space occupied by on-board systems. In addition, improvements which reduce the weight and also the manufacturing cost of the reservoir storage tanks for such systems have been long term and highly desirable goals. Thus, there has remained a clear need in the art for advancements in auxiliary fluid reservoir tank designs which promote better internal circulation of hydraulic fluid during use, are lighter in weight and less expensive to manufacture and which have an improved service life.